Human Pathogenic Dermatophytes Research Articles

Genome-wide identification and functional analysis of circRNAs in Trichophyton rubrum conidial and mycelial stages

BackgroundCircular RNAs (circRNAs) are a group of noncoding RNAs that participate in gene expression regulation in various pathways. The essential roles of circRNAs have been revealed in many species. However, knowledge of circRNAs in fungi is still not comprehensive.ResultsTrichophyton rubrum (T. rubrum) is considered a model organism of human pathogenic filamentous fungi and dermatophytes. In this study, we performed a genome-wide investigation of circRNAs in T. rubrum based on high-throughput sequencing and ultimately identified 4254 circRNAs. Most of these circRNAs were specific to the conidial or mycelial stage, revealing a developmental stage-specific expression pattern. In addition, 940 circRNAs were significantly differentially expressed between the conidial and mycelial stages. PCR experiments conducted on seven randomly selected differentially expressed (DE-) circRNAs confirmed the circularized structures and relative expression levels of these circRNAs. Based on their genome locations, most circRNAs originated from intergenic regions, unlike those in plants and animals. Furthermore, we constructed circRNA-miRNA-mRNA regulatory networks that included 661 DE-circRNAs targeting 140 miRNAs and further regulating 2753 mRNAs. The relative expression levels of two randomly selected circRNA-miRNA-mRNA axes were investigated by qRT-PCR, and the competing endogenous RNA (ceRNA) network theory was validated. Functional enrichment analysis of the target genes suggested that they were significantly involved in posttranscriptional processes and protein synthesis as well as some small-molecule metabolism processes. CircRNAs are relatively more conserved in closely related dermatophytes but rarely conserved in distantly related species. Tru_circ07138_001 is a highly conserved circRNA that was conserved in all ten dermatophytes analyzed in our study and three distantly related species. Its host gene TERG_07138 was also highly conserved in two of these distantly related species Gallus gallus and Caenorhabditis elegans. The specific role of this circRNA deserves further exploration.ConclusionsOur study is the first to provide a global profile of circRNAs in T. rubrum as well as dermatophytes. These results could serve as valuable resources for research on circRNA regulatory mechanisms in fungi and reveal new insights for further investigation of the physical characteristics of these significant human fungal pathogens.

Comparison of Antifungal Activity of Extracts of Ten Plant Species and Griseofulvin Against Human Pathogenic Dermatophytes

Background: This study was conducted to measure the antifungal activity of the extracts of 10 plant species used in traditional Iranian medicine against human pathogenic dermatophytes. Materials and Methods: In this experimental study, the leaves of these plants (Calendula officinalis , Acacia arabica, Altheae officinalis , Ginkgo biloba, Juglans regia, Osimum basilicum, Solanum nigrum, Hypericum perforatum, Urtica dioica, and Anagalis arvensis) were taken and extractions were made in methanol and were tested against Microsporum canis, Microsporum gypseum, Trichophyton mentagrophytes, Trichophyton rubrum, Trichophyton schoenleinii, and Epidermophyton floccosum . The minimum inhibitory concentration (MIC) was determined using broth macrodilution method. The effects of plants extracts were compared with those of griseofulvin. Results: Plants under review showed antifungal activity against all the dermatophytes tested with MIC values ranging from 0.001 to 0.016 mg/mL using inhibitory zone estimation, 0.3 to 12.8 mg/mL using agar dilution method and 0.2 to 12.5 mg/mL using broth dilution method. The minimum fungicidal concentration (MFC) of the extracts ranged from 0.8 to 15.62 mg/mL. Conclusions: The results obtained suggested that H. perforatum, A. arvensis, and A. arabica have anti-dermatophyte activity.

Inactivation of human pathogenic dermatophytes by non-thermal plasma

Non-thermal plasma (NTP) was tested as an in vitro deactivation method on four human pathogenic dermatophytes belonging to all ecological groups including anthropophilic Trichophyton rubrum and Trichophyton interdigitale, zoophilic Arthroderma benhamiae, and geophilic Microsporum gypseum. The identification of all strains was confirmed by sequencing of ITS rDNA region (internal transcribed spacer region of ribosomal DNA). Dermatophyte spores were suspended in water or inoculated on agar plates and exposed to NTP generated by a positive or negative corona discharge, or cometary discharge. After 15min of exposure to NTP a significant decrease in the number of surviving spores in water suspensions was observed in all species. Complete spore inactivation and thus decontamination was observed in anthropophilic species after 25min of exposure. Similarly, a significant decrease in the number of surviving spores was observed after 10–15min of exposure to NTP on the surface of agar plates with full inhibition after 25min in all tested species except of M. gypseum. Although the sensitivity of dermatophytes to the action of NTP appears to be lower than that of bacteria and yeast, our results suggest that NTP has the potential to be used as an alternative treatment strategy for dermatophytosis and could be useful for surface decontamination in clinical practice.

Isolation and identification of an extracellular subtilisin-like serine protease secreted by the bat pathogen Pseudogymnoascus destructans.

White nose syndrome (WNS) is a cutaneous fungal disease of bats. WNS is responsible for unprecedented mortalities in North American cave bat populations. There have been few descriptions of enzyme activities that may function in WNS host/pathogen interactions, while no study has isolated and described secreted proteases. To address the hypothesis that Pseudogymnoascus destructans secretes extracellular proteases that function in wing necrosis during WNS infection, the object of this study was to culture P. destructans on various media, then isolate and structurally identify those proteases accumulated stably in the culture medium. We found a single dominant protease activity on minimal nutrient broth enriched with protein substrates, which was strongly inhibited by phenylmethylsulfonyl fluoride. This P. destructans serine protease (PdSP1) was isolated by preparative isoelectric focusing and concanavalin A lectin affinity chromatography. PdSP1 showed a molecular weight 27,900 (estimated by SDS-PAGE), broad pH optimum 6-8, and temperature optimum 60°C. Structural characterization of PdSP1 by MALDI-TOF MS, Orbitrap MS/MS, and Edman amino-terminal peptide sequencing matched it directly to a hypothetical protein accession from the sequenced P. destructans genome that is further identified as a MEROPS family S8A subtilisin-like serine peptidase. Two additional isoforms, PdSP2 and PdSP3, were identified in the P. destructans genome with 90% and 53% homology, respectively. P. destructans S8A serine proteases showed closer sequence conservation to P. pannorum and plant pathogenic fungi than to human pathogenic dermatophytes. Peptide-specific polyclonal antibodies developed from the PdSP1 sequence detected the protein in western blots. These subtilisin-like serine proteases are candidates for further functional studies in WNS host-pathogen interaction.

Dermatophyte and non dermatophyte fungi in Riyadh City, Saudi Arabia

BackgroundDermatophytes are a scientific label for a group of three genera (Microsporum, Epidermophyton and Trichophyton) of fungus that causes skin disease in animals and humans. Conventional methods for identification of these fungi are rapid and simple but are not accurate comparing to molecular methods. ObjectiveThis study aimed to isolate human pathogenic dermatophytes which cause dermatophytosis in Riyadh City, Saudi Arabia and to identify these fungi by using conventional and molecular methods. MethodsThe study was conducted in Medical Complex, Riyadh and King Saud University. Samples of infected skin, hairs and nails were collected from 112 patients. Diagnosis of skin infections, direct microscopic test, isolation and identification of dermatophytes by conventional and molecular methods were carried out. ResultsThe results indicated that the tinea capitis infection had the highest prevalence among the patients (22.3%) while Tinea barbae had the lowest. In this study the identified dermatophyte isolates belong to nine species as Trichophyton violaceum, Trichophyton verrucosum, Trichophyton rubrum, Trichophyton mentagrophytes, Trichophyton schoenleinii, Trichophyton concentricum, Microsporum canis, Microsporum audouinii and Epidermophyton floccosum which cause skin infections were isolated during this study. Non dermatophyte isolates included 5 isolates from Aspergillus spp. 4 isolates from Acremonium potronii and 15 isolates from Candida spp. M. canis were the most common species (25% of isolated dermatophytes). Out of the 52 dermatophyte isolates identified by conventional methods, there were 45 isolates identified by the molecular method. ConclusionsThe results concluded that approximately M. canis caused a quarter of dermatophyte cases, tinea capitis infection was prevalent and the molecular method was more accurate than conventional methods.

Antifungal activity of a soil isolate of Pseudomonas chlororaphis against medically important dermatophytes and identification of a phenazine-like compound as its bioactive metabolite

The increasing importance of dermatophytoses and emerging resistance of dermatophytes to current synthetic antifungals have stimulated the search for safer and more effective alternative drugs from natural sources. The present study was carried out to identify antagonistic bacteria of soil origin with strong inhibitory activities on the growth of major human pathogenic dermatophytes. Antifungal activity of isolated soil bacteria was screened against the dermatophytes from three genera Microsporum (M.canis, M.gypseum), Epidermophyton (E.floccosum) and Trichophyton (T.mentagrophytes, T.rubrum, T.violaceum, T.tonsurans) by using visual plate agar assay method. A Pseudomonas chlororaphis isolate S105, identified at the species level by 16S ribosomal RNA sequence analysis, was reported as the strongest antagonistic bacterium. P.chlororaphis S105 culture supernatant (PCCS) was examined against tested dermatophytes by GY (glucose-yeast extract) broth bioassay in 6-well microplates. Antifungal compound of the bacterium was partially purified from the culture supernatant through a purification scheme of methanol extraction, Diaion HP20 ion-exchange chromatography and preparative thin layer chromatography. P.chlororaphis S105 was the most potent inhibitor of fungal growth for all tested dermatophytes with a percent inhibition ranged from 57.1% to 99.8%. The PCCS suppressed the growth of all fungi tested in the range of 18.5% to 84.8%. Partially purified antifungal compound of the bacterium was identified as a phenazine-like compound with an Rf value of 0.51. The compound inhibited fungal growth by 73.6% to 97.9% on GY broth. Fungal growth inhibition was significant for all dermatophytes tested in comparison with the controls (Anova, P<0.05). With respect to the strong inhibitory activity of P.chlororaphis against pathogenic dermatophytes reported here, it may be considered as a rich source of useful metabolites with potential application in antifungal drug discovery.

Clinico-Mycological Evaluation of Dermatophytes and Other Fungal Agents Isolated from Various Clinical Samples

Background : Human pathogenic dermatophytes are keratinophilic molds that infect human skin, nails and hairs. Three genera (Trichophyton, Micosporum and Epidermophyton) of these organisms exist: however, their preferred sites for infections vary. Current management often consists of the topical and systemic administration of antifungal agents or a combination of both. However, these approaches may not be successful in every case due to such factors as difficulty with long term application of topical medications. Despite the successful use of systemic medications side effects and drug resistance remains a major obstacle. The treatment of dermatophyte infections represents a significant cost burden. Aims and Objectives : To study the epidemiology, clinical types and mycological features of dermatophytes from various clinical samples from dermatology department, Santosh Hospital. Material and Method : A total of 100 samples were collected including infected skin, hair and nail samples for a period of six months. Before collecting the samples, 70% alcohol was applied to the infected area and ensured that it was totally dried. Skin samples were collected by scraping, nail sample by clipping and hair samples collected by using sterile forcep or scalpel. Identification was done by KOH mount, culture on SDA, pigment production, lactophenol cotton blue staining and biochemical tests and slide culture techniques. Results : Dermatophytosis was manifested clinically more in the age group 21 - 30 years age. Tinea corporis was the predominant clinical presentation followed by Tinea cruris. Tinea capitis was the predominant clinical presentation in children and Tinea manuum was the commonest clinical type found in female patients. In the present study the male to female ratio was found 1.5 : 1. Majority of patients were belonged to the low socio-economic status. Trichophyton rubrum was the predominant pathogen followed by the Trichophyton mentagrophytes. Conclusion : Tinea corporis was found the most common clinical type of dermatophytosis and Trichophyton rubrum was found the most common fungal isolate in this part of Uttar Pradesh.

Broad spectrum antidermatophytic drug for the control of tinea infection in human beings

During antifungal evaluation of various plant extracts, free and bound flavonoids of Piper betle were found to be most effective as an antidermatophytic against human pathogenic dermatophytes Trichophyton rubrum, Trichophyton mentagrophytes, Microsporum gypseum and Candida albicans. Dermatophytic fungi cause both superficial and internal mycoses. These mycoses, although normally not lethal, are unpleasant and difficult to cure and cause considerable financial losses. Earlier workers prove that allopathic drugs are still found effective against dermatomycoses, but these drugs could not be accepted as a routine treatment for every case, because they are expensive and require long treatment. It is almost unaffordable by middle and lower class people. In view of such prospects and constraints, our aim was to explore more new compounds of plant origin for controlling dermatophytic infections. Author explored water, methanolic and flavonoid extracts for screening as antidermatophytic agent. Plant extracts that showed good results in vitro were selected for clinical studies. The study may give cheaper treatment for medium and lower class patients suffering with tinea and may provide them much relief. Well-established paper disc method was used for the screening of different extracts of their antidermatophytic activity. Moreover, it did not exhibit any adverse side effect on mammalian skin. Flavonoids in the form of ointment Pi be I and Pi be II were subjected to topical testing on patients attending out patients department of S.M.S. Hospital, Jaipur, India. Patients were diagnosed as tinea corporis, tinea capitis, tinea manum or tinea pedis. All patients showed positive potassium hydroxide (KOH) results at the beginning of trial. Patients between the ages of 3 months to 58 years were enrolled. At the end of treatment, while 64% of patients cured completely, 24% showed significant improvement and 12% showed little improvement from the disease. Allopathic treatment took 4-8 weeks when compared with only 1-5 weeks taken by Pi be I and Pi be II ointments. The ointment, thus not only showed maximum affectivity but was also found to be a better and cost effective alternative to allopathic drug for tinea infections. The acceptability of alternative medicines, particularly herbal medicines, has now become a critical need of the times.

Solanum melongena: A potential source of antifungal agent

The antifungal activity of Solanum melongena leaf, extracted with petroleum ether, chloroform, methanol and water was evaluated against three human pathogenic dermatophytes namely Trichophyton mentagrophytes, T. rubrum and T. tonsurans and two opportunistic fungi Candida albicans and Trichosporon beigelii. Maximum yield of plant components was 4.32 g, extracted in water and minimum 1.07 g in petroleum ether from 150 g of dry plant material. Except water extract, all the extracts possessed significant antifungal property. All the test pathogens showed highest sensitivity towards chloroform extract, exhibiting maximum inhibition zone diameter of 50.0 mm in T. mentagrophytes and minimum 30.0 mm in C. albicans at 2 × 10(5) μg/ml concentration. Chloroform extract at lower concentration 2.5 × 10(4) μg/ml was inhibitory for all the test pathogens, exhibiting inhibition zone diameter 21.0 mm against T. tonsurans and 15.0 mm against C. albicans and T. beigelii. The activity of the different solvent extracts against the test pathogens in terms of inhibition zone diameter in decreasing order was as followsChloroform extract > Petroleum ether extract > Methanol extract for T. mentagrophytes, T. rubrum and T. tonsurans.Chloroform extract > Methanol extract > Petroleum ether extract for C. albicans and T. beigelii.

Differential gene expression in the pathogenic dermatophyte Arthroderma benhamiae in vitro versus during infection

Although dermatophytes are the most common agents of superficial mycoses in humans and animals, the molecular basis of the pathogenicity of these fungi is largely unknown. In vitro digestion of keratin by dermatophytes is associated with the secretion of multiple proteases, which are assumed to be responsible for their particular specialization to colonize and degrade keratinized host structures during infection. To investigate the role of individual secreted proteases in dermatophytosis, a guinea pig infection model was established for the zoophilic dermatophyte Arthroderma benhamiae, which causes highly inflammatory cutaneous infections in humans and rodents. By use of a cDNA microarray covering approximately 20-25 % of the A. benhamiae genome and containing sequences of at least 23 protease genes, we revealed a distinct in vivo protease gene expression profile in the fungal cells, which was surprisingly different from the pattern elicited during in vitro growth on keratin. Instead of the major in vitro -expressed proteases, others were activated specifically during infection. These enzymes are therefore suggested to fulfil important functions that are not exclusively associated with the degradation of keratin. Most notably, the gene encoding the serine protease subtilisin 6, which is a known major allergen in the related dermatophyte Trichophyton rubrum and putatively linked to host inflammation, was found to be the most strongly upregulated gene during infection. In addition, our approach identified other candidate pathogenicity-related factors in A. benhamiae, such as genes encoding key enzymes of the glyoxylate cycle and an opsin-related protein. Our work provides what we believe to be the first broad-scale gene expression profile in human pathogenic dermatophytes during infection, and points to putative virulence-associated mechanisms that make these micro-organisms the most successful aetiological agents of superficial mycoses.

In Vitro Antifungal Activity of Polysulfides-Rich Essential Oil of Ferula Latisecta Fruits against Human Pathogenic Dermatophytes

The increase in dermatophytoses and the fact that some patients do not respond well to therapy make it necessary to find new antifungal agents. As part of our ongoing studies on medicinal plants from Iran, we studied antidermatophytic activities of Ferula latisecta essential oil, which had shown considerable antifungal activity in preliminary antimicrobial screening. Antifungal activity was evaluated by determination of MIC values using the agar dilution method on type strains of Candida albicans and dermatophytes. The composition of the oil was characterized by GC and GC/MS analyses. The essential oil was rich in polysulfides (75.2%) and exhibited good activity against Trichophyton rubrum and T. verrucosom for about three weeks, with a MIC value 96 μg/mL. The oil showed antifungal activity, especially against dermatophytes, and the activity is probably related to the sulfur-containing components of the oil. This study has identified that the polysulfides-rich essential oil of Ferula latisecta fruits has activity against a range of human pathogenic dermatophytes, justifying future clinical trials to validate its use as a therapeutic alternative for dermatophytosis.

Keratinophilic fungi inhabiting floor dusts of student houses at the South Valley University in Egypt

Keratinophilic fungi include true fungi that vigorously degrade keratin as well as a number of important human pathogenic dermatophytes. We identified 41 species and one variety belonging to 19 genera in 50 floor dust samples following culture on Sabouraud’s dextrose agar medium at 28°C. Dermatophytes and closely related fungi were represented by six species—Aphanoascus fulvescens, Aphanoascus sp., Arthroderma cuniculi, Chrysosporium lucknowense, Gymnoascus uncinatus and Trichophyton rubrum. There were 35 species and one variety of other fungal species, with members of Aspergillus and Penicllium being the most prevalent. Twenty-seven species and 1 variety belonging to 14 genera were identified from 24 dust samples gathered at 2-week intervals from male student housing at El-Kenose during January–December 2005 that had been cultured on Sabauraud’s dextrose agar at 28°C. The monthly counts of keratinophilic fungi showed irregular fluctuations, with a peak in April and the lowest point in November. Dermatophytes and closely related fungi were represented by Aphanoascus fulvescens, Aphanoascus sp., Chrysosporium lucknowense, Gymnoascus uncinatus, and Trichophyton rubrum. In conclusion, the study reports the incidences of some dermatophytes found in the floor dust of student houses of South Valley University, Egypt.

Antifungal activity of Ocimum gratissimum towards dermatophytes

The development of more effective and less toxic antifungal agents is required for the treatment of dermatophytosis. Plants and their preparations have been used as medicines against infectious diseases. Extracts of Ocimum gratissimum leaves were investigated for in vitro antifungal activity, using agar dilution technique against dermatophytes. The extracts (hexane, chloroform fractions, the essential oil and eugenol) produced antifungal activities against Microsporum canis, M. gypseum, Trichophyton rubrum and T. mentagrophytes. Trichophyton rubrum, the most common aetiological agent of dermatophytosis in Goiânia, state of Goiás, Brazil, was also the most susceptible dermatophyte. The hexane fraction and eugenol were the most active. Hexane fraction inhibited the growth of 100% of dermatophytes at a concentration of 125 microg ml(-1), while eugenol inhibited the growth of 80% of dermatophytes at this same concentration. These results show that extracts of O. gratissimum are active in vitro against human pathogenic dermatophytes.

Isolation of Bioactive Compounds from Aspergillus terreus

A new metabolite, 6-(4’-hydroxy-2’-methyl phenoxy)-(-)-(3R)-mellein (1) was isolated from the ethyl acetate extract of Aspergillus terreus culture medium along with three known isocoumarin derivatives, (-)-(3R)-6-methoxymellein (2), (-)-(3R)-6,7-dimethoxymellein (Kigelin) (3) and (3R, 4R)-6,7-dimethoxy-4-hydroxymellein (4). Metabolites 1 and 4 showed significant activity against human pathogenic dermatophytes, Microsporum canis and Trichophyton longifusus. Metabolite 1 also exhibited potent antioxidant activity. The structures of metabolites were characterized on the basis of spectroscopic techniques. 13C NMR data of metabolites 2 - 4 are also being reported for the first time

Screening forin vitroAntifungal Activities of some Indole Alkaloids

Several indole alkaloids were tested by the agar dilution technique on a panel of human pathogenic fungi, yeasts, and dermatophytes. Our results indicate that the most active compounds possess a beta-carboline skeleton and that the presence of a 3-4 double bond enhances the activity. Our results also show that antifungal activities are not linked to the cytotoxic, antimicrobial or antiparasitic properties.